1. Field of the Invention
The invention relates to power combining, and in particular, to RF power combining.
2. Description of the Related Art
It is often desirable to combine the output power of more than one RF amplifier. For example, the output power requirements for a particular system may be higher than practical from a cost, packaging, or efficiency point of view. For example, relatively low voltage RF devices can typically operate relatively efficiently at RF speeds, but this can limit the available power from a single RF device. Accordingly, there can be a need to combine the output power of multiple RF amplifiers.
Combining power at radio frequencies is not a simple task. At radio frequencies, impedance mismatches can result in reflections, which can cause an uneven frequency response of the system, which is typically undesirable.
Typically, a structure for a power splitter can also be used for a power combiner and vice versa. Examples of structures include resistive combiners, rat-race couplers, Wilkinson power splitters, and magic tees.
Examples of prior techniques for combining can be found in U.S. Pat. Nos. 2,698,381 to Robertson-Shersby-Harvie; 2,847,517 to Small; 2,874,276 to Dukes et al.; 3,091,743 to Wilkinson; 4,316,160 to Dydyk; and 4,367,445 to Dydyk. Other related information can be found in the following: David M. Pozar, “Microwave Engineering,” Third Edition, 2005; T. C. Edwards, “Foundations for Microstrip Circuit Design,” 1981; and Andrei Grebennikov, “RF and Microwave Power Amplifier Design,” 2005.